Semiconductor devices are commonly found in modern electronic products. Semiconductor devices vary in the number and density of electrical components. Discrete semiconductor devices generally contain one type of electrical component, e.g., light emitting diode (LED), small signal transistor, resistor, capacitor, inductor, and power metal oxide semiconductor field effect transistor (MOSFET). Integrated semiconductor devices typically contain hundreds to millions of electrical components. Examples of integrated semiconductor devices include microcontrollers, microprocessors, charged-coupled devices (CCDs), solar cells, and digital micro-mirror devices (DMDs).
Semiconductor devices perform a wide range of functions such as signal processing, high-speed calculations, transmitting and receiving electromagnetic signals, controlling electronic devices, transforming sunlight to electricity, and creating visual projections for television displays. Semiconductor devices are found in the fields of entertainment, communications, power conversion, networks, computers, and consumer products. Semiconductor devices are also found in military applications, aviation, automotive, industrial controllers, and office equipment.
Semiconductor devices exploit the electrical properties of semiconductor materials. The atomic structure of semiconductor material allows its electrical conductivity to be manipulated by the application of an electric field or base current or through the process of doping. Doping introduces impurities into the semiconductor material to manipulate and control the conductivity of the semiconductor device.
A semiconductor device contains active and passive electrical structures. Active structures, including bipolar and field effect transistors, control the flow of electrical current. By varying levels of doping and application of an electric field or base current, the transistor either promotes or restricts the flow of electrical current. Passive structures, including resistors, capacitors, and inductors, create a relationship between voltage and current necessary to perform a variety of electrical functions. The passive and active structures are electrically connected to form circuits, which enable the semiconductor device to perform high-speed calculations and other useful functions.
Semiconductor devices are generally manufactured using two complex manufacturing processes, i.e., front-end manufacturing, and back-end manufacturing, each involving potentially hundreds of steps. Front-end manufacturing involves the formation of a plurality of die on the surface of a semiconductor wafer. Each semiconductor die is typically identical and contains circuits formed by electrically connecting active and passive components. Back-end manufacturing involves singulating individual semiconductor die from the finished wafer and packaging the die to provide structural support and environmental isolation. The term “semiconductor die” as used herein refers to both the singular and plural form of the words, and accordingly can refer to both a single semiconductor device and multiple semiconductor devices.
One goal of semiconductor manufacturing is to produce smaller semiconductor devices. Smaller devices typically consume less power, have higher performance, and can be produced more efficiently. In addition, smaller semiconductor devices have a smaller footprint, which is desirable for smaller end products. A smaller semiconductor die size can be achieved by improvements in the front-end process resulting in semiconductor die with smaller, higher density active and passive components. Back-end processes may result in semiconductor device packages with a smaller footprint by improvements in electrical interconnection and packaging materials.
FIG. 1a shows a conventional semiconductor package 10 with a semiconductor die 12 having an active surface 14. Conductive layer 16 are formed on active surface 14. An insulating layer 18 is formed over active surface 14 and conductive layer 16. An insulating layer 20 is formed over insulating layer 18 and conductive layer 16. Conductive layer or redistribution layer (RDL) 22 is formed over insulating layer 20 and electrically connected to conductive layer 16. An insulating layer 24 is formed over insulating layer 20 and conductive layer 22. An under bump metallization (UBM) layer 26 is formed over insulating layer 24 and electrically connected to conductive layer 22. A bump 28 is formed over UBM layer 26.
FIG. 1b is a plan view of semiconductor die 12 with a plurality of bumps 28. Bump 28a is enclosed by surrounding bumps 28b. In order to make electrical connection to bump 28a, conductive layer 22 is routed between adjacent surrounding bumps 28b. The routing arrangement of conductive layer 22 between adjacent surrounding bumps 28b requires additional area on semiconductor die 12. The adjacent surrounding bumps 28b must be spaced further apart to permit the routing of conductive layer 22 between the bumps. In existing semiconductor die being converted from wire bond interconnect to RDL routing, as well as new design die layouts, routing conductive layer 22 between adjacent surrounding bumps 28b makes die space allocation difficult.